Tubular cartons, including gable top cartons are widely employed for beverages and other liquids. A tubular carton is formed from a single blank of paperboard material with an array of score lines about which the paperboard material is folded to form the carton.
One desirable tubular carton which has a gable top is shown in U.S. Pat. No. 4,558,814 which issued to Ihde on Dec. 17, 1985, and is assigned to the assignee of the subject application. U.S. Pat. No. 4,558,814 discloses a gable top carton having first through fourth generally rectangular side panels consecutively articulated to one another, and a generally rectangular interior side edge flap articulated to the fourth panel. The interior side edge flap is sometimes referred to in the industry as the glue flap. First through fourth top and bottom flaps are articulated to the opposed ends of the first through fourth side panels, respectively, while top and bottom seam flaps are articulated to the opposed ends of the side seam flap. The blank for forming the carton disclosed in U.S. Pat. No. 4,588,814 further comprises a reinforcing tab extending from both the side seam flap and the bottom seam flap. The reinforcing tab has no score lines and is rabbeted to define a thickness less than the remainder of the blank. The unscored reinforcing tab is folded over adjacent portions of the side seam flap and the bottom seam flap to perform a reinforcing function at the bottom corner of the resulting carton.
Despite the many desirable features of tubular cartons in general, and the particular structural features shown in the above identified U.S. Pat. No. 4,558,814 (the disclosure of which is incorporated herein by reference), it has been found that in certain instances, liquids stored in a tubular carton are likely to wick into the paperboard material generally along the interior side edge thereof. The wicking could cause small amounts of liquids stored in the prior art gable top cartons to travel through the fibrous paperboard material. The wicking generally is not sufficient to cause spoilage of the product stored therein or to sufficiently reduce the volume. However, wicking of certain colored liquids, such as fruit juices, has been known to cause a clearly visible observable discoloration along the seal area of the prior art gable top carton. This discoloration is noticeable and often objectionable to consumers.
Accordingly, it is an object of the subject invention to provide an apparatus and process for sealing the interior side edge of a carton blank to prevent wicking of liquid material.
It is another object of the subject invention to provide a method and apparatus for sealing the carton side edge of a carton blank to prevent wicking of liquids through the paperboard material and into the seal areas of the carton.
It is still a further object of the subject invention to provide a new and improved apparatus and process for sealing the side edge of a gable top carton blank prior to erection of the tabular carton.